Question

Sendo $<var>x^{2}</var>$ + $<var>y^{2}</var>$=65 e x * y=28, então x +y é?

Answer 1

$x^{2}+y^{2}=65 \\ xy=28$

$(x + y)^{2}=x^{2}+2xy+y^{2}$
$(x + y)^{2} = (x^{2} + y^{2}) + 2xy$
$(x + y)^{2}=65 + 2*28$
$(x + y)^{2}=65+56$
$(x + y)^{2}=121 \\ x + y =\pm\sqrt{121} \\ x+y=\pm11$